Abstract Biochar is an eco-friendly soil amendment that has been demonstrated to have significant potential for regulating soil properties and immobilizing heavy metals. In this study, a meta-analysis was performed to synthesize global data from 41 peer-reviewed studies (2012–2024) and evaluate the effects of biochar on soil chemistry and copper (Cu) mobility. The results revealed that biochar application increased the soil pH, cation exchange capacity (CEC), and electrical conductivity (EC) while decreasing the available and TCLP-extractable Cu contents. Biochar with an ash content > 60% elevated the soil pH by ≥ 32.4%, and biochar with a specific surface area (SSA) of 50–100 m²/g enhanced the CEC by ≥ 183%. Low nitrogen content (N% 7.5) and oxygen content (O% >20%) significantly reduced the available Cu (≥ 37.72% and ≥ 22.31%, respectively) and TCLP-extractable Cu (≥ 34.97% and ≥ 24.07%, respectively) contents. Notably, the largest improvement in pH occurred in highly acidic soils (initial pH = 3), and biochar with a pH > 7.5 most effectively reduced Cu mobility. Notably, the ability of biochar to immobilize Cu was independent of the initial soil pH. The immobilization of copper by biochar primarily involved several mechanisms, including precipitation, surface complexation with oxygen-containing functional groups, ion exchange, and physical adsorption within its porous structure. These findings provide actionable insights for the sustainable management of soil by highlighting the ability of biochar to increase soil fertility and remediate Cu-contaminated soils through chelation with Cu functional groups.
Teng et al. (Thu,) studied this question.